The present invention relates to a microencapsulated Lewis acid where a Lewis acid is confined in a network of a polymer gel. The microencapsulated Lewis acid is in a condition where a Lewis acid is fixed on the surface or the inside of a polymer capsule and confined in certain room to function as a catalyst of organic syntheses.
The development of catalysts supported on organic polymers has hitherto been a very important theme of organic syntheses. The reason for this is that the catalysts supported on organic polymers are very economical in view of the preparation and the separation from reaction products and the industrial application thereof is expected. Furthermore, although some of catalysts supported on polymers have been reported so far, the activity of such catalysts is low as compared with carrier-free catalyst and highly active catalysts supported on organic polymers has been very difficult to realize.
On the other hand, attention is directed to Lewis acids because of the characteristic catalytic activity and selectivity of reactions thereof and in addition, the Lewis acids promote catalytic reactions under molder conditions, thus the Lewis acids being recognized to be industrially very useful. However, the Lewis acids decompose in aqueous solutions and are difficult to recover and recycle, and these facts are common to Lewis acid catalysts supported on polymers. For example, although an aluminum chloride catalyst supported on a crosslinked organic polymer is known and can be easily recovered from the reaction system after using once, the catalyst is difficult to recover from the reaction system after using twice or more to make the recycling thereof impossible.
Thus, the conventional Lewis acid catalysts are not necessarily easy in the preparation of reaction systems, the separation from reaction products, and the recovery and recycling thereof. The catalysts supported on organic polymers also are difficult to recover and recycle to make the use thereof uneconomic.
The invention, accordingly, aims at overcoming the technical limit of the conventional catalysts supported on polymers and in addition, at solving problems attendant upon the preparation of reaction systems, the separation from reaction products, and the recovery as to the Lewis acid catalysts having great industrial usefulness, thus to provide novel microencapsulated Lewis acids supported on polymers and catalysts formed of these.
The invention provides as the first invention a microencapsulated Lewis acid characterized in that s Lewis acid is supported through coordinate bonds on a microcapsule formed of an organic polymer.
In relation to the first invention, the invention also provides a microencapsulated Lewis acid as particles or aggregates thereof as the second invention; a microencapsulated Lewis acid where the organic polymer is a substantially non-crosslinked polymer prepared by addition polymerization as the third invention; a microencapsulated Lewis acid where the organic polymer is a substantially non-crosslinked polymer containing aromatic rings as the fourth invention; a microencapsulated Lewis acid where the organic polymer is a substantially non-crosslinked polymer containing benzene rings as the fifth invention; a microencapsulated Lewis acid where the organic polymer is a substantially non-crosslinked polymer containing aromatic rings on the side chains as the sixth invention; a microencapsulated Lewis acid where the organic polymer is a substantially non-crosslinked polymer containing benzene rings on the side chains as the seventh invention; and a microencapsulated Lewis acid where the Lewis acid is trifluoromethanesulfonate of a rare earth metal as the eighth invention.
The invention further provides as the ninth invention Lewis acid catalysts that are characterized by being formed of the aforesaid microencapsulated Lewis acids of the first through eighth inventions.
Furthermore, the invention provides as the tenth invention a process for preparing a microencapsulated Lewis acid characterized in that a Lewis acid is supported through coordinate bonds on microcapsules simultaneously on forming the microcapsules from an organic polymer by a microencapsulation process and as the eleventh invention a process of preparing the microencapsulated Lewis acid wherein the microencapsulation process is a phase separation process.
In the microencapsulated Lewis acid supported through coordinate bonds on an organic polymer according to the invention, the Lewis acid is arranged on the surfaces of capsules and exposed on the polymer in a condition where the acid is confined and enveloped in complicated room of the inside of capsules, thus to participate in reactions as a catalyst.